Adhesive bindings for composite components are presently not certified for being used as exclusive joining element in primary supporting components of an aircraft. The main reason for that is that the adhesive bonding greatly depends on manufacturing parameters like impurity or surface preparation. All these influencing parameters may result in a weakened bonding or in debindering of the adhesive bonding. As to avoid this, preventing propagation of cracks is presently attempted. Alternatively, it is attempted to prevent cracks from growing.
As secondary adhesive bindings shall be used in composite components for primary supporting components, it is favorable that possible damages (debindering) can be found by persons without any specific knowledge within few flight cycles or during regular maintenance work. So far, providing sensors in the various connections is necessary for any monitoring of the state of structures (structural health monitoring). This results in complicated architectures, so that the advantages of composite connections, namely their light weight, cost-effectiveness, and durability are reduced.
For example, EP 2 431 156 A1 discloses using magnetostrictive parts in the connection to be monitored, wherein strains in the magnetostrictive parts caused by damages in the connection can be detected by an external sensor.
WO 2012/141779 A1 discloses a connection in which a fabric and an electric network with sensors are included which serve for monitoring the state of the connection.